The Whirlpool Galaxy, also known as Messier 51a (M51a) or NGC 5194, is an interacting grand-design spiral galaxy with a Seyfert 2 active galactic nucleus. It lies in the constellation Canes Venatici, and was the first galaxy to be classified as a spiral galaxy. This galaxy has a smaller companion galaxy known as Messier 51b (M51b) or NGC 5195 which may have passed through the main disk of M51 about 500 to 600 million years ago.
This subject was captured using the fast imaging technique where 8,709 subframes of 4 seconds each were captured in broadband and then star aligned and averaged together using Pixinsight's FastIntegration process to increase SNR and reduce the effects of light pollution on the final image. 175 subframes of 120 seconds each were captured using a dual band filter to bring out the hydrogen alpha regions of the galaxy to be continuum subtracted and then added to the final image. Both the RGB and Ha were drizzled at a scale of 2 times with a drop shrink of 0.9 to enhance the resolution.
This subject was captured from my backyard in a suburb south of Chicago which is Bortle 8.5.
Revision B is a close-up of the M51 galaxy
https://www.astrobin.com/lmaor8/#rB
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